Anthony Rizzo was the last left-handed third baseman in Major League Baseball, appearing in one game at the hot corner for the Chicago Cubs in 2017.
Before Rizzo took to the left side of the infield in the bottom of the ninth inning in a Cubs loss to the Cincinnati Reds at Wrigley Field on August 22, 2017, the most recent lefty to man third was Mario Valdez of the Chicago White Sox in 1997.
Like Rizzo, Valdez’s stint on the left side of the infield lasted all of one inning.
Indeed, the occurrence of left-handed third basemen in MLB is exceedingly rare, owing nearly entirely to the cross-body positioning involved.
In general, third basemen will be fielding balls hit to their left side, since ball to the right will mostly be in foul territory. That makes it advantageous for their glove to be on that side — on their left hand, that is.
Left-handers, of course, wear their gloves on their right hands, which would often have them turning their backs to batters and other fielders as the attempt to range left.
Even more cumbersome for lefties is the need to throw to second or first, which requires them to plant their feet and pivot in order to get a solid base for launch.
Right-handers are already facing their infield mates as they field the ball, and the thrown is a natural extension of their in-progress strides.
The complete list of left-handed third basemen in MLB history: Anthony Rizzo, Mario Valdez, Don Mattingly, Terry Francona, Mike Squires (14 times), Charlie Grimm, and George Sisler.